Modifications in neutrino counting due to additional gauge bosons

We examine the possible influence of additional heavy neutral gauge bosons ($Z_1^0$) on attempts at neutrino counting in $e^{+}$ $e^{\mathrm{-}}$ annihilation below the $Z_1^0$ (≃93 GeV) resonance. A large class of two-$Z^0$-boson models is examined. We find that the apparent shift in the number of neutrinos, $N_{\nu }$, due to the extra $Z^0$ boson in these models is never larger than ≃0.4 if $N_{\nu }$=3 and somewhat smaller if $N_{\nu }$=4. Thus we should not expect a large ‘‘error’’ in neutrino counting to result in these extensions of the standard model.